Transmission is a machine in the power transmission system, which provides power control applications. Often the term refers to only the gearbox that uses gears and toothbrakes to provide speed and torque conversion from rotating resources to other devices.
In English English, the term transmission refers to the entire drivetrain, including clutch, gearbox, drive shaft (for rear-wheel drive), differential, and final drive shaft. However, in American English, the term refers more specifically to the gearbox only, and the use of details is different.
The most common use is in motor vehicles, where the transmission adjusts the output of the internal combustion engine to the driving wheel. Such machines must operate at relatively high rotational speeds, which are not suitable for starting, stopping, and slower travel. The transmission reduces the engine's higher speed to a slower wheel speed, increasing the torque in the process. Transmission is also used on pedal bikes, fixed engines, and where different rotation speeds and torques are adjusted.
Often, the transmission has dual gear ratios (or just "gears") with the ability to switch between them as speed varies. This switch can be done manually (by operator) or automatically. Directional (forward and backward) controls may also be provided. Single-ratio transmission also exists, which only changes the speed and torque (and sometimes direction) of the motor output.
In motor vehicles, the transmission is generally connected to the engine crankshaft via a flywheel or clutch or fluid clutch, in part because the internal combustion engine can not run below a certain speed. The output of the transmission is transmitted through the driveshaft to one or more differentials, which drive the wheels. While the differential can also provide gear reduction, the main purpose is to allow the wheels at both ends of the shaft to rotate at different speeds (important to avoid wheel slippage on alternating) as it changes the direction of rotation.
Conventional dental/belt transmission is not the only mechanism for speed/torque adaptation. Alternative mechanisms include torque converters and power transformations (eg diesel-electric transmissions and hydraulic drive systems). The hybrid configuration also exists. Automatic transmission uses the valve body to move the tooth using fluid pressure in response to speed and throttle input.
Video Transmission (mechanics)
Description
Initial transmissions include right-angle drives and other gearing in windmills, horse-powered devices, and steam engines, to support pumping, grinding, and lifting.
Most modern gearboxes are used to increase torque while reducing the speed of the main driving shaft output (eg motor crankshaft). This means that the output shaft of the gearbox rotates at a slower rate than the input shaft, and this reduction in speed results in a mechanical advantage, increasing the torque. The gearbox can be set to do otherwise and provide increased shaft speed with reduced torque. Some simple gearboxes only change the physical rotation direction of power transmission.
Many typical car transmissions include the ability to select one of several gear ratios. In this case, most gear ratios (often called "gears") are used to slow down engine output speed and increase torque. However, the highest gear may be the type of "overdrive" that increases the speed of the output.
Maps Transmission (mechanics)
Usage
Gearboxes have found use in a variety of different applications - often stationary, such as wind turbines.
Transmission is also used in agricultural equipment, industry, construction, mining and automotive. In addition to the regular transmission equipped with gears, the equipment utilizes the use of hydrostatic drives and adjustable electric-speed drives.
Simple
The simplest transmissions, often called gearboxes to reflect their simplicity (though complex systems are also called gearboxes in everyday language), provide a reduction of teeth (or, more rarely, speed increases), sometimes simultaneously with right angular changes in direction shaft (usually in helicopter, see picture). This is often used in PTO-powered agricultural equipment, since the axial PTO shaft is in conflict with the ordinary need for a vertical axle (as with a rotary mower), or horizontally extending from one side of the appliance to another (As with fertilizer spreaders, hitting cutting machine, and saw foraging). More complex tools, such as silage choppers and snowblowers, have drives with output in more than one direction.
The gearbox in the wind turbine converts the slow and high torque rotation from the turbine into a much faster electric generator rotation. It's much bigger and more complicated than a PTO gearbox in farm equipment. They weigh several tons and typically contain three stages to achieve an overall gear ratio of 40: 1 to over 100: 1, depending on the size of the turbine. (For aerodynamic and structural reasons, larger turbines must rotate more slowly, but all generators must rotate at the same speed of several thousand rpm.) The first stage of the gearbox is usually planetary gears, for compactness, and for distributing large torque turbines over more gears from the lower speed shaft. The endurance of this gearbox has been a serious problem for a long time.
Regardless of where they are used, these simple transmissions all share important features: gear ratios can not be changed when in use. It was repaired when the transmission was built.
For this type of transmission that addresses this problem, see Continuous variable transmission, also known as CVT.
Multi-ratio system
Many applications require the availability of dual gear ratios. Often, this is to make it easier to start and stop mechanical systems, although another important need is to maintain good fuel efficiency.
Automotive basics
The need for in-car transmissions is a consequence of the internal combustion engine characteristics. Machines typically operate over a range of 600 to about 7000 rpm (though this varies, and usually less for diesel engines), while the car wheels rotate between 0 rpm and about 1800 rpm.
Furthermore, this machine delivers the highest torque and uneven power output across the entire rotation range that produces band torque and power band. Often the greatest torque is required when the vehicle moves from rest or runs slowly, while maximum power is required at high speed. Therefore, a system that changes the engine output is required to supply high torque at low speed, but also operate at highway speeds with the motor still operating within its limits. Transmission performs this transformation.
The dynamics of a car vary with speed: at low speeds, acceleration is limited by the inertia of the mass of motor vehicles; while at roaming or the maximum speed of wind resistance is a dominant barrier.
Many transmissions and gears are used in automotive and truck applications contained in cast iron cases, although more often aluminum is used to lose weight especially in cars. There are usually three axes: the main shaft, the drive shaft, and the idler shaft.
Mainshaft extends outside the casing in both directions: the input shaft toward the engine, and the output shaft to the rear axle (in the rear-wheel drive car.The front-wheel drive generally has engine and transmission mounted transversely, the differential being part of the transmission assembly.) The shaft suspended by the main bearing, and separated to the input end. At the split point, the pilot bearing holds the shaft together. The gears and grips rise in the main axle, the gears become free to turn relative to the main axle except when attached by the grip.
Manual
Manual transmission consists of two basic types:
- Simple but powerful synchronous sliding-mesh system, where the straight set of straight tooth teeth rotates freely, and should be synchronized by a suitable machine operator with a lap to the road speed, to avoid noise clashes and damage gears
- Current, ubiquitous constant mesh gearboxes, which may include an unsynced, or synchronized/synchromesh system, where usually a diagonal (or sometimes either straight-cut, or double-helical) helical cut is usually constantly "fused" together, and the dog clutch is used to change gears. In the synchromesh box, the friction cones or "synchro-rings" are used in addition to the dog clutch to match the rotation speeds of both sides of the transmission (expressed) before making full mechanical engagement.
The first type is standard in many ancient cars (in addition to epicyclic and multi-coupling systems) prior to the development of constant-mesh and hydraulic-epicyclic automatics manuals, older and still found heavy-duty trucks used in some farming equipment. The latter is a modern standard for manual transport and semi-automatic on-and off-road transmission, although it can be found in many forms; for example, straight cuts that are not synchronized in horse racing apps or super-heavy, non-synchro helical applications in most heavy trucks and certain classic cars and cars (eg Fiat 500), and partially or fully synchronized with helices in almost all passenger cars modern manuals and light trucks.
Manual transmissions are the most common type outside of North America and Australia. They are cheaper, lighter, usually deliver better performance, but the latest automatic transmissions and CVT provide better fuel savings. It is a habit for new drivers to learn, and tested, on cars with manual gearshift. In Malaysia and Denmark all cars are used for testing (and therefore, almost all of which are used for instruction as well) have manual transmissions. In Japan, Philippines, Germany, Poland, Italy, Israel, Netherlands, Belgium, New Zealand, Austria, Bulgaria, England, Ireland, Sweden, Norway, Estonia, France, Spain, Switzerland, Australia state in Victoria, Western Australia and Queensland , Finland, Latvia, Lithuania, and the Czech Republic, passing tests using automated cars do not entitle the driver to use manual cars on public roads; a manual car test is required. Manual transmissions are much more common than automatic transmissions in Asia, Africa, South America and Europe.
Manual transmissions can include synchronized and non synchronized gearing. For example, reverse gear is usually not synchronized, because the driver is only expected to do so when the vehicle is stuck. Many older (up to the 1970s) cars also do not have synchronization on the first gear (for various reasons - the cost, usually "shorter" overall gearing, the engine usually has more low-end torque, extreme wear on the first tooth synchronization is often used...), which means it also can only be used to move away from stops unless the driver becomes adept at declaring a double and has a particular need to regularly descend to the lowest gear.
Some manual transmissions have a very low ratio for first gear, called creeper tooth or grandmother's teeth . Such teeth are usually not synchronized. This feature is common in pickup trucks tailored to trailer, farm, or construction work. During normal road usage, the truck is usually driven without the use of creeper teeth at all, and the second gear is used from the beginning of the stand. Some off-road vehicles, most notably Jeep Willy and his descendants, also have granny first's transmissions either as standard or option, but this function is now more commonly provided by low-pass transfer gearboxes attached to normal fully synchronized transmissions.
Out of sync
Some commercial apps use an unsynchronized manual transmission that requires a skilled operator. Depending on the country, many local, regional, and national laws govern the operation of this type of vehicle ( see Commercial Driver License ). This class may include commercial, military, agricultural, or engineering vehicles. Some may use a combination of types for multi-purpose functions. An example is the power take-off (PTO) of the tooth. This type of non-synchronous transmission requires an understanding of the range of gears, torque, engine power, and clutch functions and multi-functional shifters. Also see the Double-clutching section, and Clutch-brake from the main article. Float shifting is the process of gearshift without the use of clutch.
Automatic
Most modern North American cars, and some European and Japanese cars have automatic transmissions that choose the appropriate gear ratio without operator intervention. They primarily use hydraulics to select teeth, depending on the pressure provided by the fluid inside the transmission assembly. Instead of using a clutch to engage transmission, the flywheel liquid, or torque converter is placed between the engine and the transmission. It is possible for the driver to control the number of gears used or to choose backwards, although the proper control of the teeth used may or may not be possible.
Auto transmission is easy to use. However, in the past, some automatic transmissions of this type had a number of problems; they are complex and expensive, sometimes have reliability issues (which sometimes cause more costs in repairs), are often less fuel-efficient than their manual counterparts (due to "slippage" in the torque converter), and their shift times are more slow than manuals makes them uncompetitive for racing. With the advancement of modern automatic transmission has changed.
Efforts to improve the fuel efficiency of automatic transmissions include the use of torque converters that lock beyond a certain speed or higher gear ratios, remove power loss, and overworked gears that automatically move above a certain speed. In older transmissions, both technologies can interfere, when conditions are such that they repeatedly enter and exit as speed and load factors such as class or wind are slightly different. Computerized transmissions today have complex programming that maximizes fuel efficiency and eliminates interference. This is mainly due to electronic progress rather than mechanical, although the improvement of CVT technology and the use of automatic coupling has also helped. Some cars, including the 2013 Subaru Impreza and 2012 Honda Jazz models sold in the UK, actually claim a slightly better fuel consumption for the CVT version than the manual version.
For certain apps, the slippage attached to the automatic transmission can be beneficial. For example, in a drag race, the automatic transmission allows the car to stop with the engine at high rpm ("stall speed") to allow for a very fast launch when the brakes are released. In fact, a common modification is to increase the speed of the transmission stall. It is even more advantageous for a turbocharged engine, where the turbocharger must keep rotating at high rpm by a large flow of exhaust to maintain the push pressure and eliminate the turbo lag that occurs when the throttle suddenly opens on the idling machine.
Semi-auto
A hybrid form of transmission in which an integrated control system handles clutch manipulation automatically, but the driver can still - and may be required - take manual control of dental selection. This is sometimes called "manual without clutch", or "manual automatic" transmission. Many of these transmissions allow the driver to fully delegate the gear transfer option to the control system, which then effectively acts as if it were an ordinary automatic transmission. They are generally designed using "internal" manual transmissions, and when used in passenger cars, have a synchromesh helical constant mesh gear set that is operated.
The initial semi-automatic system uses a variety of mechanical and hydraulic systems - including centrifugal coupling, torque converter, electro-mechanical (and even electrostatic) and servo/solenoid controlled couplings - and automatic control-declutching schemes when moving tooth levers, pre-selector controls, centrifugal clutches with sequential-drum shifts that require drivers to lift throttles for successful shifts, etc.-- and some smaller than automatic lock-ups of automatic torque converters with manual gear selection.
Most modern implementations, however, are standard manual transmissions or slightly modified (and sometimes modified automatically - even including some CVT cases with fixed "false tooth ratio"), with a servo controlled clutch and a shift under the computer's central machine command. This is intended as a combined replacement option for both the more expensive and less efficient "normal" automatic system, and for drivers who prefer manual shifts but are no longer able to operate the clutch, and users are encouraged to leave fully automatic drive shift levers most of the time , it only involves manual-sequential mode for sporty driving or when otherwise necessary.
Specific types of transmission include: Easytronic, Tiptronic and Geartronic, as well as systems used as standard across all ICE-powered Smart-MCC vehicles, and on step-by-step scooters like the Honda Super Cub or Suzuki Address.
The dual-clutch transmission takes turns using two internal sets, each with its own clutch, so the "gearchange" actually consists of only one clutch involved as another release - providing a smooth "smooth" shift (or roaring reuptake of) electrical transmission. Each clutch-mounted shaft carries half of the total input gear (with shared output shaft), including a synchronized dog clutch system that has selected which set of ratios are most likely to be required in the next shift, under the computerized control command of the system. This special type of transmission includes: Direct-Shift Gearbox.
There is also a sequential transmission that uses drum rotation to change the gear, just like a complete manual motorcycle. It can be designed with a manual or automatic clutch system, and can be found both in cars (especially tracks and race cars rally), motorcycles (usually light "step-thru" types of urban utility bikes, for example, Honda Super Cub) and quadbikes with separate reversing gear involved), the latter two usually using a scooter-centrifugal centrifugal clutch.
Bicycle gear
Bikes usually have a system to choose different gear ratios. There are two main types: derailleur gear and hub gear. This type of derailleur is the most common, and most visible, using sprocket gears. Usually there are several gears available in the rear sprocket assembly, which are attached to the rear wheels. Some additional sprockets are usually added to the front assembly as well. Multiplying the number of sprocket gears in front with the numbers back gives the number of gear ratios, often called "speed".
The Hub gear uses an epicyclic gearing and is enclosed inside the rear wheel axle. Due to the small space, they typically offer fewer different speeds, although at least one has reached 14 gear ratios and Fallbrook Technologies manufactures transmissions with unlimited technical ratios.
Several attempts have been made to fit the bike with a closed gearbox, providing clear advantages for better lubrication, dirt sealing and shifting. This is usually associated with the drive shaft, since traditional chain gearboxes (such as hub teeth) still have many weaknesses for the derailleur of the open chain. The bicycle gearbox is flanked in a box replacing the traditional bottom bracket. Requirements for modified frames have been a serious disadvantage to its application. One of the latest attempts to provide the gearbox for the bike is 18 speed Pinion P1.18. It provides a closed gearbox, but it is still a traditional chain. When mounted to the rear suspension bike, it also retains a chain-like chain-derailleur jockey rail, albeit without a low ground clearance derailleur.
Causes of bicycle gearing failure include: worn teeth, damage caused by faulty chain, thermal expansion damage, tooth decay due to excessive paddling power, interference by foreign objects, and loss of lubrication due to negligence.
Uncommon type
Double clutch transmission
This setting is also sometimes known as a direct-shift gearbox or gearhift gearbox. It seeks to combine the advantages of conventional manual shifts with modern automatic transmission quality by providing different grips for odd and even speed pickup teeth. When changing gears, engine torque is transferred from one tooth continuously, thereby providing smooth and smooth gear changes without loss of power or jolting of the vehicle. The gear selection may be manual, automatic (depending on the throttle/speed sensor), or the 'sports' version that combines both options.
Continuous variable
The continuously variable transmission (CVT) is a transmission in which the ratio of the two-axle rotational speed, as the input shaft and the output shaft of the vehicle or other machine, may vary continuously within the given range, providing an infinite number of possible ratios. CVT allows the driver or computer to choose the connection between engine speed and wheel speed in a continuous range. This can provide better fuel savings if the engine keeps running at a single speed. Transmission, in theory, is capable of providing a better user experience, without ups and downs in engine speed, and the jerk feels when changing gears poorly.
CVT is increasingly found in small cars, and especially high-engine vehicles or hybrids. On this platform, torque is limited because the electric motor can provide torque without changing the speed of the engine. By leaving the engine working at a speed that produces the best mileage for a given operating condition, overall mileage can be increased through a system with smaller fixed gear numbers, where the system may operate at peak efficiency only for small ranges of speed. CVT is also found in agricultural equipment; due to the high torque nature of these vehicles, the mechanical gears are integrated to provide traction power at high speeds. The system is similar to a hydrostatic gearbox, and at 'shuffle speed' depends entirely on the hydrostatic drive. The German tractor manufacturer, Fendt, pioneered the technology, developing the 'Vario [1] transmission.
Unlimited Variables
IVT is a special type of CVT that includes not only unlimited number of gears ratio , but also an "unlimited" range . This is a phrase shift, actually refers to a CVT capable of entering a "zero ratio", where the input shaft can change without any output shaft movement while remaining in the gear. The gear ratio in this case is not "unlimited" but otherwise "undefined".
Most (if not all) IVTs are produced from a combination of CVT with an episyclic dental system with a fixed ratio. The combination of fixed tooth episyclic ratios with a specific matching ratio in addition to CVT yields a zero output. For example, consider transmission with epicyclic gears set to 1: -1 tooth ratio; reverse gear 1: 1. When the CVT side is set to 1: 1, the two ratios will add zero output. IVT is always involved, even during zero output. When the CVT is set to a higher value operate conventionally, by increasing the ratio of the forward.
In practice, epicyclic teeth can be set to the lowest possible ratio of CVT, if reversing is not required or handled through other means. Reversal can be inserted with the epicyclic gear ratio adjustment somewhat higher than the lowest CVT ratio, providing various reverse ratios.
Power variables
Electric Variable Transmission (EVT) combines transmission with an electric motor to give a single CVT illusion. In general implementation, the gasoline engine is connected to a traditional transmission, which in turn connects to the planetary carrier of the epicyclic gear system. The electric motor/generator is connected to the "sun" center of the tooth, which is usually not driven in a typical epicyclic system. Both resources can be incorporated into the transmission output at the same time, dividing the power between them. In a typical example, between a quarter and a half of the machine's power can be incorporated into a solar fixture. Depending on its implementation, the transmission in front of the epicyclic system can be greatly simplified, or eliminated altogether. EVTs are able to continuously modulate the ratio of output/input speeds such as CVT mechanics, but offer different benefits because it can also apply power from two different sources to one output, as well as potentially dramatically reduce overall complexity.
In typical implementation, the transmission gear ratio and the epicyclic system are set to the ratio of general driving conditions, say the highway speed for the car, or the speed of the city for the bus. When the driver presses the gas, the associated electronics interpret the pedal position and immediately set the gasoline engine to the RPM which gives the best mileage for the setting. Since gear ratios are usually set away from the maximum torque point, this arrangement will usually result in a very bad acceleration. Unlike gasoline engines, electric motors offer efficient torque in various RPM options, and are very effective at low settings where inefficient gasoline engines. By varying the electrical load or supply on a motor attached to the sun gear, additional torque may be provided to make up for the low torque output of the engine. When the vehicle accelerates, power to the motor is reduced and eventually ends, giving the illusion of CVT.
The canonical example of EVT is Hybrid Synergy Drive from Toyota. This implementation does not have a conventional transmission, and solar equipment always receives 28% of the torque from the engine. This power can be used to operate all the electrical load in the vehicle, recharge the battery, turn on the entertainment system, or run the air conditioning system. Each remaining power is then fed back into the second motor which drives the output of the drivetrain directly. At highway speeds, these additional generator/motor lines are less efficient than just turning the wheels directly. However, during acceleration, the power lines are much more efficient than machines that operate away from the point of torque. GM uses a similar system in the Allison Bus powertrain hybrid and Tahoe and Yukon pickup trucks, but it uses a two-speed transmission in front of the epicyclic system, and solar equipment receives nearly half of the total power.
Indirect
Electricity
The electric transmission transforms the mechanical strength of the engine (s) into electricity by an electric generator and converts it back to engine power by an electric motor. An electric or electronic speed-adjustable drive control system is used to control motor speed and torque. If the generator is driven by a turbine, such arrangement is called turbo-electric transmission. Likewise the installation supported by a diesel engine is called diesel-electric.
The diesel-electric arrangement is used in many railroad locomotives, ships, large mining trucks, and some bulldozers. In this case, each driven wheel is equipped with its own electric motor, which can be electrically powered to provide the necessary torque or power output for each wheel independently. This results in a much simpler solution for some wheels driven in a very large vehicle, where the drive shaft will be much larger or heavier than the power cord that can provide the same amount of power. It also enhances the ability to allow different wheels to run at different speeds, which is useful for steering wheels in large construction vehicles.
Hydrostatic
- See also continuously variable Transmission & gt; Hydrostatic CVT
The hydrostatic transmission transmits all power hydraulically, using hydraulic machine components. They are similar to electrical transmissions, but use hydraulic fluids as electrical distribution systems rather than electricity.
The transmission input drive is a central hydraulic pump and the final drive unit is/is a hydraulic motor, or hydraulic cylinder (see: swashplate ). Both components can be placed physically far apart on the machine, which is connected only with a flexible hose. Hydrostatic driving systems are used on excavators, lawn tractors, forklifts, crane systems, heavy lifting equipment, agricultural machinery, earth transfer equipment, etc. Arrangements for motor vehicle transmissions may be used on Ferguson F-1 P99 racing cars around 1961.
Human Friendly Transmission from Honda DN-01 is hydrostatic.
Hydrodynamics
If the hydraulic pump or hydraulic motor utilizes the hydrodynamic effect of the fluid flow, ie the pressure due to a change in the momentum of the fluid as it flows through the blades in the turbine. Pumps and motors typically consist of spinning blades without seals and are usually placed in close proximity. The transmission ratios can be made vary by the use of a rotary propeller, an effect similar to varying the pitch of the aircraft propellers.
Torque converter in automotive auto transmission is, in its own right, a hydrodynamic transmission. Hydrodynamic transmission is used in many passenger-train vehicles, which do not use electrical transmission. In this application the advantage of a smooth power delivery may be greater than the decrease in efficiency caused by the loss of turbulence energy in the fluid.
See also
Note
References
Further reading
- Harald Naunheimer; Peter Fietkau; G Lechner (2011). Automotive transmission: basics, selection, design and applications (2nd ed.). Jumper. ISBNÃ, 9783642162138 . Retrieved 2014-04-29 .
External links
- Manual Transmission Operations, (YouTube), Weber State University, Odgen 2012
Source of the article : Wikipedia
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